In a typical air atomization type spray gun, paint or other liquid coating material is discharged under pressure through an orifice in a fluid tip. The liquid orifice is surrounded by an annular opening defined between the fluid tip and an air cap. Compressed air supplied to the air cap discharges through the annular opening for atomizing the discharged liquid. The air cap also normally includes other orifices for discharging supplementary air jets for enhancing atomization and for controlling and shaping the spray pattern. Typically, the fluid tip is attached to the end of the spray gun barrel. The air cap is positioned over the fluid tip and an annular retainer ring is positioned over the air cap and screwed to the end of the barrel to retain the air cap on the barrel.
During use of the spray gun, it is sometimes necessary to remove the air cap to service the spray gun. For example, it may be necessary to clean or to change the fluid tip. In an industrial application, the spray gun is often attached either to a fixed mount or to a reciprocator or even to an industrial robot located in a spray booth. The spray gun may be mounted to point in a downward direction. When the air cap retainer ring is removed, the loose air cap may fall if the operator is not careful. Many industrial spray booths have a grate on the floor. If the air cap is dropped, it may be lost through the grate or it may be damaged. In either case, loss or damage to the air cap results in added operating expense and increased down time for the spray equipment.
Similar problems may occur with servicing other types of spray gun nozzles. For example, in an air assisted airless atomization type spray gun, a fluid tip and an air cap are free to fall when a retainer ring is removed during disassembly and assembly.